ALEXANDRIA, Va. — A U.S. Army veteran was charged Thursday with joining up with an al-Qaida group to fight against the government of Syrian President Bashar al-Assad.

Eric Harroun, 30, of Phoenix was charged in U.S. District Court in Alexandria with conspiring to use a weapon of mass destruction — specifically, a rocket propelled grenade launcher — outside the U.S.

According to an FBI affidavit, Harroun, who served two years in the Army before being medically discharged, was engaged in military action in Syria, siding with rebel forces against the Syrian government, from January to March of this year.

Harroun told FBI investigators that he traveled to Turkey in November hoping to join the Free Syrian Army, a rebel group. In January, he crossed the border and made contact with the Free Syrian Army, which outfitted him two Russian rifles, according to the affidavit.

Within days, Harroun participated in an attack on a Syrian army encampment that was carried out jointly by the Free Syrian Army and the al-Nusrah Front, commonly known as "al-Qaida in Iraq" and designated a terrorist group by the U.S., according to the affidavit.

After that battle, Harroun retreated in the back of an al-Nusrah truck. Harroun told the FBI that at the al-Nusrah camp, he was initially treated like a prisoner but was later accepted by the other members and participated in several attacks with them, according to the affidavit.

Harroun said al-Nusrah fighters would ask him why the U.S. had designated them as terrorists, according to the affidavit.

Harroun used RPG launchers in the attacks and once, on his Facebook page, claimed credit for downing a Syrian helicopter. According to the affidavit, Harroun told the FBI that he shot an estimated 10 people in his various battles, though he was unsure if he had ever killed anyone.

On the Facebook page, Harroun also stated that "the only good Zionist is a dead Zionist" and that he intended to travel to the Palestinian territory because of Israeli atrocities there, according to the affidavit. The affidavit states that Harroun served in the Army from 2000 to 2003, when he received a medical discharge after he was injured in a car accident.

The federal public defender was appointed to represent Harroun at an initial public appearance Thursday, and a detention hearing was scheduled for Tuesday. Assistant U.S. Attorney Andrew Peterson said Harroun faces up to life in prison.

Harroun flew back to the U.S. Wednesday through Dulles International Airport. He was arrested after being questioned by FBI agents there.

The public defender for the Eastern District of Virginia, Michael Nachmanoff, declined comment Thursday, saying he had not yet had time to review the case in any depth.

Last year, Nachmanoff's office represented a northern Virginia man, Mohamad Soueid, who pleaded guilty to spying on U.S.-based Syrian dissidents on behalf of the Assad regime. Soueid said he was motivated to help the Syrian government because of his fear that Islamic extremists would take hold in Syria if Assad's secular regime were overthrown.

Harroun is not charged with providing material support to a terrorist group, but instead conspiring to use a weapon of mass destruction outside the U.S., a law that applies to U.S. nationals operating anywhere in the world. The statute makes no distinction or exception for an individual who may be fighting a hostile regime.